I cannot start my Win XP VM with existing settings as VirtualBox 3.1.0 claims VT-x not detected.I used it for a long time on my ThinkPad T61p with T7500 processor (see support in Intel doc: http://ark.intel.com/VTList.aspx)

Ok, playing with settings some more: This happens when I select 2 Processors, which seems to be legal (green bar).Switching back to 1 processor the VM starts fine.

Something is wrong here - Either it is not possible to assign 2 processors to Win XP guests with a dual core host processor (which the settings show as fine) or VT-x detection is broken.Let me know if I can provide more info to help. Thanks.

I suspect that the problem is that the previous VBox version did not support SMP and that you had Windows installed with a single processor kernel.Anyway does yous bios support hardware virtualization, and is it turned on?

Good tip re BIOS - VT-x seems to have been disabled during the last BIOS update and I re-enabled it now.Unfortunately I am still getting the same error. This happens immediately when starting the VM - I would think long before it hits the Windows client OS.The host OS is Windows 7 Enterprise.I just googled to see if there is a tool to check if VT-x is present but didn't come up with a tool. Any recommendation?

Unfortunately my client OS now crashes right when booting into the logon screen (instead of showing the screen it recycles indefinitely from boot)I can start into Safe Mode and uninstalled Guest Additions 3.1 but it is still crashing (it booted fine with 3.0.12 allowing me to install 3.1 but broken since initial restart)I'll play around a bit more and hope I can fix this. I have been using VB for well over a year now and never had an issue with an update throughout 3.0.x.

Ok, in the meantime I rolled back to 3.0.12 as, unfortunately, I have some work to do and this is my main development setup

Attached are the logs and 1.8 settings file zipped up. Unfortunately the Blue Screen disappears after a microsecond before cycling so can't take any info from it. The crashes continued after uninstalling VBox additions in Safe Mode. Hope this means something. Looking forward to getting my hands on the 3.1 features!

Did you happen to reboot after you did the install?What I see is an error saying that it can not read from the medium.That is after it has loaded it all up.You may need to send this to the DEVs via bugtracker. Link is below my post.

I attached another log and settings file in case you are interested. These are done with a new 3.1 VM from scratch.1st attempt is setting 2 processors, which gives the No VT-x error.2nd attempt is simply reducing the client processor number to 1, which seems to be passing fine (I did not complete the XP install but it loaded the install wizard up just fine)

The log says that VT-x is locked or not available. You don't have anything else running in VT-x do you, like XP mode?If no then I would send these to bugtracker. It makes no sense that it would work in 3.0.12 and not is 3.1.X unless there was a regression issue.

Great! Looks like this worked. I am now running the guest with 2 CPUs. Thanks!

FAQ wrote:Another hint: after enabling VT-X/AMD-V in the BIOS you might need to switch the PC off completely, unplug it, or remove laptop battery for a minute. Ea:Reboot the Host and go into the BIOS disable vt-x, save BIOS settings, pause machine after bios boot messagespower down the Host (unplug power cord!)start the Host and go into the BIOS enable vt-x, save BIOS settings, pause machine after bios boot messagespower down the Host (unplug power cord!)Boot the Host.